HUMAN FORCING ON REGIONAL AQUATIC SYSTEMS : A LONG TERM BIOGEOCHEMICAL PERSPECTIVE

A river system with its associated ponds, lakes and reservoirs, its estuary and the adjacent coastal marine area form a continuum of aquatic ecosystems of regional extension. The biogeochemical functioning of this continuum is controlled by climatic and hydromorphological forcing as well as by inputs of material from the watershed. These latter inputs reflect the organisation of material cycles in the terrestrial systems of the catchment, which, in most part of the world, have been deeply reshaped by human civilisations. Human development also often involved large modifications of the hydromorphological -and more recently climatic- forcing. With the aid of an idealised biogeochemical model of aquatic continuums, we will try to characterize how the most important historical trends in the way biogenic (C,N,P, Si) and anthropogenic (metals, xenobiotics) material cycle within terrestrial systems at regional scale, as a result of human development, controlled aquatic systems functioning, under different climatic conditions.